The subject matter disclosed herein relates to magnetic resonance imaging (MRI) “compatible” or “conditional” mobile computing devices. More specifically, tablet computers suitable for use by a patient or technologist in a MRI environment are disclosed.
As is known to those skilled in the art, an MRI system generates a strong magnetic field and detects the faint nuclear magnetic resonance (NMR) signals given off by nuclei in the presence of the magnetic field. The NMR signals are received by antennas, also known as coils, and transmitted to the MRI scanner for reconstruction into an MRI image. In order to provide a clear image, it is desirable to minimize electromagnetic interference from outside sources.
As a result, MRI scanners are located within a shielded room, also known as the scan room. The scan room includes walls, or panels, which typically incorporate radio frequency (RF) shielding within the wall. The controller for the MRI scanner is typically located in an adjacent control room. A window permits an operator to observe activity within the scan room from the adjacent control room.
However, the MRI environment creates numerous challenges that make conventional electronic devices unusable in the MRI environment. Most electronic devices employ magnetic parts or utilize ferrous components that are susceptible to the scanner's static magnetic field. The static magnetic field generated by the MRI scanner may, at a minimum, interfere with these devices, and at worst, pull the devices into the bore of the scanner, potentially injuring the patient. Further, non-magnetic metal components may be susceptible to electromagnetic interference once exposed to the MRI's strong dynamic magnetic fields, causing the device to malfunction or even destroying it. The electronic device itself could also interfere with the sensitive MRI imaging. For example, long wire runs typically connecting electrical controllers in the control room with audio-visual devices in the scan room may function as antennas. These long wire runs raise the potential of both radiating electromagnetic interference detectable by the MRI scanner due to signals transmitted on the wire and receiving interference from the MRI scanner which degrades the signal provided to the patient.
There is a desire to place electronic devices within the MRI environment for many reasons. One example of such need is during functional MRI (fMRI) scanning. In fMRI scanning, images must be taken of the brain while the brain is stimulated and unstimulated. Different types of stimulus are typically measured including visual stimuli in the form of images or videos shown to the patient and auditory stimuli such as audible sounds. However, delivering audio-visual stimuli to the patient has been a challenge in the MRI environment without electronic devices. Other uses of electronic devices within the MRI environment may include viewing the patient's facial responses, viewing real-time MRI waveforms and adjusting the scan prescription, patient charting, and audio-visual displays for patient comfort and entertainment (this is particularly useful for children and patients with claustrophobia), all from within the scan room.
Historically, these limitations have been overcome by removing electrical devices from the scan room completely or by removing electronic components from the scan room. One such solution for delivering audio-visual signals to the MRI environment is the use of fiber optic cables running between the control room and displays within the MRI environment. Other solutions include projection technology to project an image from the control room into the scan room, often with the assistance of mirrors and projection screens. However, the visual monitors are normally installed outside the bore and are difficult for the patient to see, providing a less than ideal solution. Audio solutions have included the use of pneumatic headphones, which eliminate any electronic components but compromise the quality of the sound.